Search PubMed⌕ Search

Biomedical subjects

J L Williams

Publications and source records attributed to J L Williams.

At least 37 records · Page 2Linked to original sources
PubMed2005

The use of marker-assisted selection in animal breeding and biotechnology.

Improvement of livestock has focused on the selective breeding of individuals with superior phenotypes. With the development of increasingly advanced statistical methods that maximise selection for genetic gain, this simple approach has been extremely successful in increasing the quantity of agricultural output. However, information now available on the organisation and functioning of the genome could be used in breeding programmes to improve a range of traits. Many traits are under the control of several genetic loci, each of which contribute to the variation in the trait and hence are called quantitative trait loci (QTL). While genetic markers for QTL that are linked to the trait gene could be used to choose animals for selective breeding programmes, the most effective markers are the functional mutations within the trait genes. Strategies to identify markers for traits and the application of these markers are described by reference to examples of loci that control a range of different traits.

Animals↗
PubMed2004

Optimal screw diameter for interference fixation in a bone tunnel: a porcine model.

The study investigates the optimal interference screw dimensions required to secure a tendon graft in a bone tunnel. A standard 8 mm pig flexor-tendon graft was inserted into a standard open-ended 8 mm bone tunnel of a porcine distal femur and secured using either 7 mm, 8 mm or 9 mm diameter metal interference screws (Arthrex Inc, Naples, FL). The construct was tested to failure using a Shimadzu ASG 10KN Universal Material Testing Machine (Shimadzu, Tokyo, Japan). Load and mode of construct failure were recorded for 37 individual constructs. There was no significant difference in the load at failure between the 7 mm screw (192 N; range 151-232) and 8 mm screw (181 N; range 150-212) (p>0.05). There was a significant difference between the 7 mm screw and the 9 mm screw (109 N; range 67-151) (p=0.006) and between the 8 mm screw and the 9 mm screw (p=0.015). When using a 9 mm screw, 100% of the constructs failed by cut out of the graft at the tunnel opening. The 7 mm constructs failed by slippage of the tendon from the bone tunnel in 83% of cases, with only 17% failing by cut out at the tunnel opening. The 8 mm constructs demonstrated a mixture of failure modes, with slippage occurring in 58% of cases, cut out in 38% and failure of the graft substance in one case (4%). In this model, screw diameters equal to or 1 mm less than the tunnel/tendon diameter provides better fixation than using a screw 1 mm larger. The mode of failure differs for each of these screws.

Animals↗
PubMed2004

Physical and linkage mapping of mammary-derived expressed sequence tags in cattle.

This study describes the physical and linkage mapping of 42 gene-associated markers developed from mammary gland-derived expressed sequence tags to the cattle genome. Of the markers, 25 were placed on the USDA reference linkage map and 37 were positioned on the Roslin 3000-rad radiation hybrid (RH) map, with 20 assignments shared between the maps. Although no novel regions of conserved synteny between the cattle and the human genomes were identified, the coverage was extended for bovine chromosomes 3, 7, 15, and 29 compared with previously published comparative maps between human and bovine genomes. Overall, these data improve the resolution of the human-bovine comparative maps and will assist future efforts to integrate bovine RH and linkage map data.

Animals↗
PubMed2004

Application of AFLP technology to radiation hybrid mapping.

We have investigated the use of AFLP technology as a tool for the high throughput enrichment of Radiation Hybrid (RH) maps. The 3000 rad TM112 bovine RH panel was assayed with 37 EcoRI/TaqI AFLP primer combinations. The number of selective nucleotides used during PCR was increased to seven, to reduce the complexity of the AFLP profile and minimise the overlap between hamster and bovine bands co-amplified from hybrid cell clones. Seven-hundred-forty-seven bovine AFLP bands were amplified that could be distinguished following electrophoresis. Repeatability was tested within and between laboratories on independent template preparations and an error rate of 1.3% found. Two-point linkage analysis clustered 428 AFLP fragments in 39 linkage groups of at least 4 markers. Multi-point maps were constructed for 5 sample linkage groups. The study demonstrated that the AFLP approach could be used to rapidly screen for the most informative clones during panel construction and to increase the number of markers on RH maps, which could be useful for joining linkage groups formed by other markers. The use of AFLP markers as anchor points between existing RH maps and other physical maps, such as BAC contigs, is also discussed.

Animals↗
PubMed2004

Breed relationships and definition in British cattle: a genetic analysis.

The genetic diversity of eight British cattle breeds was quantified in this study. In all, 30 microsatellites from the FAO panel of markers were used to characterise the DNA samples from nearly 400 individuals. A variety of methods were applied to analyse the data in order to look at diversity within and between breeds. The relationships between breeds were not highly resolved and breed clusters were not associated with geographical distribution. Analyses also defined the cohesiveness or definition of the various breeds, with Highland, Guernsey and Jersey as the best defined and most distinctive of the breeds.

Animals↗
PubMed2004

Mapping and transcription profiling of CASP1, 3, 6, 7 and 8 in relation to caspase activity in the bovine cumulus-oocyte complex.

So far 12 caspases have been described in mouse and human while only one (CASP13) is known in cattle. The aim of this study was to (1) search for other bovine caspases by reverse transcription and polymerase chain reaction (RT-PCR) and (2) examine the presence of bovine caspase mRNA and active protein in the cumulus-oocyte complex. Five caspases (1, 3, 6, 7 and 8) were identified, partially cloned and sequenced. Four of them were mapped. Differential transcription of the caspase genes was detected, but no active caspase protein was found in diverse bovine oocytes. Cumulus granulosa cells (CGC) contain CASP1, 6, 7 and 8 mRNA and active caspase protein. The presence of caspase mRNA and active caspase proteins in CGCs suggests the occurrence of apoptosis in cumulus-oocyte complex, while caspase activation is blocked in fresh oocytes and therefore caspase transcription cannot be used to predict the oocyte developmental capacity.

Animals↗
PubMed2004

An expanded comparative map of bovine chromosome 27 targeting dairy form QTL regions.

At present, the density of genes on the bovine maps is extremely limited and current resolution of the human-bovine comparative map is insufficient for selection of candidate genes controlling many economic traits of interest in dairy cattle. This study describes the chromosomal mapping of 10 selected gene-associated markers to bovine linkage and radiation hybrid maps to improve the breakpoint resolution in the human-bovine comparative map near two previously identified quantitative trait loci for the linear type trait, dairy form. Two regions of conserved synteny not previously described are reported between the telomeric region of bovine chromosome 27 (BTA27) and human chromosome 3 (HSA3) p24 region and between the HSA4q34.1 region and BTA8. These data increase the number of genes positioned on the bovine gene maps, refine the human-bovine comparative map, and should improve the efficiency of candidate gene selection for the dairy form trait in cattle.

Animals↗
PubMed2004

Characterization and chromosome localization of a processed pseudogene related to the bovine laminin receptor gene family.

A bovine BAC clone containing a processed laminin receptor pseudogene (LAMR1P) has been isolated and characterized. A 2,901-bp sequence was produced from the clone, of which 1,187 bp represented seven identifiable exon-like domains, but no intervening sequences. The pseudogene sequence reveals several transversions and transitions, as well as insertions and deletions. A premature stop codon motif is present at nucleotide position 115 located in the exon-2-like domain. Physical mapping of the gene was performed by FISH and RH panel mapping and assigned LAMR1P to BTA4q24-->q26 with the closest linkage to BM6458 (19 cR, LOD score of 11.6). The functional laminin receptor putatively plays an important role in the transmission of bovine spongiform encephalopathy (BSE). In this process, the receptor supposedly acts as the binding site for prion proteins to enter mammalian cells. Considering the existence of several human laminin receptor pseudogenes forming a complex family, any knowledge of even pseudogene sequences might be helpful to isolate the functional bovine laminin receptor gene.

Animals↗
PubMed2003

A comparison of newborn stylized and tomographic models for dose assessment in paediatric radiology.

Establishment of organ doses from diagnostic and interventional examinations is a key component to quantifying the radiation risks from medical exposures and for formulating corresponding dose-reduction strategies. Radiation transport models of human anatomy provide a convenient method for simulating radiological examinations. At present, two classes of models exist: stylized mathematical models and tomographic voxel models. In the present study, organ dose comparisons are made for projection radiographs of both a stylized and a tomographic model of the newborn patient. Sixteen separate radiographs were simulated for each model at x-ray technique factors typical of newborn examinations: chest, abdomen, thorax and head views in the AP, PA, left LAT and right LAT projection orientation. For AP and PA radiographs of the torso (chest, abdomen and thorax views), the effective dose assessed for the tomographic model exceeds that for the stylized model with per cent differences ranging from 19% (AP abdominal view) to 43% AP chest view. In contrast, the effective dose for the stylized model exceeds that for the tomographic model for all eight lateral views including those of the head, with per cent differences ranging from 9% (LLAT chest view) to 51% (RLAT thorax view). While organ positioning differences do exist between the models, a major factor contributing to differences in effective dose is the models' exterior trunk shape. In the tomographic model, a more elliptical shape is seen thus providing for less tissue shielding for internal organs in the AP and PA directions, with corresponding increased tissue shielding in the lateral directions. This observation is opposite of that seen in comparisons of stylized and tomographic models of the adult.

Computer Simulation↗
PubMed2003

Signatures of selection? Patterns of microsatellite diversity on a chromosome containing a selected locus.

This paper explores patterns of genetic diversity near a locus known to have been under selection. The myostatin gene (GDF-8) has been shown to be associated with double muscling, a phenotype selected for in a number of cattle breeds. We examined population genetic parameters for microsatellite loci at varying distances from GDF-8 in double-muscled (DM) and non-double-muscled (non-DM) cattle breeds in order to assess patterns of diversity. A theoretical analysis was also performed to predict the patterns of diversity expected under different scenarios. We found differences in the patterns of heterozygosity, allele diversity and linkage disequilibrium between DM and non-DM breeds. However, there were some exceptions to the predicted patterns. These are discussed in light of the histories of the breeds and the potential for using microsatellite diversity for mapping trait genes in livestock populations.

Animals↗
PubMed2003

Sequence variation in the bovine and ovine PRNP genes.

A resequencing approach was adopted to identify sequence variants in the PRNP gene that may affect susceptibility or resistance to bovine spongiform encephalopathy. The entire PRNP gene (>21 kb) was sequenced from 26 chromosomes from a group of Holstein-Friesian cows, as well as exon 3 of PRNP (>4 kb) from a further 24 chromosomes from six diverse breeds. We identified 51 variant sequences of which 42 were single nucleotide polymorphisms and nine were insertion/deletion (indel) events. The study was extended to exon 3 of the sheep PRNP gene where 23 sequence variants were observed, four of which were indels. The level of nucleotide diversity in the complete bovine PRNP gene was pi = 0.00079, which is similar to that found at the bovine T-cell receptor alpha delta joining region (pi = 0.00077), but somewhat less than that observed for the bovine leptin (pi = 0.00265). Sequence variation within exon 3 of PRNP in both cattle (pi = 0.00102) and sheep (pi = 0.00171) was greater than that for the complete PRNP gene, with sheep showing greater sequence variation in exon 3 than cattle. The level of sequence variation reported here is greater than previously thought for the bovine PRNP gene in cattle. This study highlights the contribution that recombination plays in increasing allelic diversity in this species.

Amyloid↗
PubMed2003

Characterization and mapping of bovine dopamine receptors 1 and 5.

A cDNA encoding the bovine dopamine receptor 1 (DRD1) was isolated from a bovine cDNA library, cloned and completely sequenced. The coding region showed 93 and 91% sequence identity on DNA level and 96 and 94% on protein level with its respective porcine and human orthologs. The bovine DRD1 and dopamine receptor 5 (DRD5) were mapped, respectively, to BTA10 and 6 by radiation hybrid mapping. One SNP was found in DRD1 and four in DRD5. Using polymerase chain reaction-restriction fragment length polymorphism, 11 different European cattle breeds were screened for the presence of the DRD1 and DRD5 substitutions. Allele frequencies for DRD1 and DRD5 alleles were very similar across all the breeds examined. Allele frequency discrepancies were found between Belgian Blue beef breed and the other breeds.

Animals↗
PubMed2003

Mapping and SNP analysis of bovine candidate genes for meat and carcass quality.

The chromosomal localization of 13 bovine genes was determined using radiation hybrid (RH) mapping. The RH mapping data were in agreement with published data using either linkage, somatic cell hybrids or in situ hybridization. Mutation analysis using single-stranded conformational polymorphism, restriction fragment length polymorphism (RFLP) and sequencing revealed 13 SNPs in four different genes, namely carboxypeptidase E (CPE), uncoupling protein 2 (UCP2), single-minded (Drosophila) homologue 1 (SIM1) and methallothionein IIa (MT2A). With the exception of one mutation in CPE, all other mutations are either silent or are situated in an intron. The polymerase chain reaction RFLP was used on unrelated animals from different cattle breeds for determing allelic distribution.

Animals↗
PubMed2003

A new mutation in the coding region of the bovine leptin gene associated with feed intake.

An experimental cattle population was screened for polymorphisms in the leptin gene and five SNPs were found in the regions containing the coding sequences. The association of these polymorphisms with feed intake and fat-related traits was evaluated. The results suggest an association between a polymorphism in exon 2, described here for the first time, and feed intake. Individuals with genotype A/T at this position had 19% greater mean feed intake than individuals with genotype A/A. There was also evidence for a link between leptin haplotypes and some fat-related traits.

Animals↗